Radiotherapy system and radiotherapy planning apparatus

Abstract

According to one embodiment, a radiotherapy apparatus generates counting data as a count value of photons included in a preset energy region based on an output signal from an observation detector. The radiotherapy apparatus generates medical image data based on the counting data.

What is claimed is: 
     
       1. A radiotherapy system comprising:
 a first radiation source configured to generate radiation for observation; 
 a first detector configured to detect radiation generated from the first radiation source and transmitted through a subject; 
 a second radiation source configured to generate radiation for radiotherapy; 
 a counting processing unit configured to generate first counting data, the first counting data including count value of photons included in a preset energy range based on a first output signal from the first detector; and 
 an image generating unit configured to generate first medical image data based on the first counting data, wherein 
 the counting processing unit comprises 
 a data acquisition unit configured to acquire the first output signal from the first detector in a photon counting mode and generate first acquired data based on the first output signal, and 
 an extraction unit configured to extract first counting data with a reduced noise component from the first acquired data by using a threshold set to an energy value corresponding to a window band which has an incident X-ray peak energy at its center and an energy width corresponding to an energy resolution, the reduced noise component being of an energy region lower than the threshold. 
 
     
     
       2. The radiotherapy system of  claim 1 , further comprising an index value counting unit configured to calculate an index value associated with a body motion amount of a subject by using the first medical image data. 
     
     
       3. The radiotherapy system of  claim 2 , further comprising:
 a determination unit configured to determine whether the index value is not more than a threshold; and 
 a controller configured to stop emission of radiation from the second radiation source when it is determined that the index value is not less than the threshold. 
 
     
     
       4. The radiotherapy system of  claim 2 , further comprising:
 a detection unit configured to detect a timing at which the index value becomes larger than a threshold and a timing at which the index value becomes smaller than the threshold; and 
 a controller configured to stop emission of radiation from the second radiation source when the index value becomes larger than the threshold and emit radiation from the second radiation source when the index value becomes smaller than the threshold. 
 
     
     
       5. The radiotherapy system of  claim 1 , wherein counting data associated with an incidence event of scattered rays of radiation from the second radiation source is removed from the first counting data. 
     
     
       6. The radiotherapy system of  claim 1 , further comprising:
 a second detector configured to detect radiation generated from the second radiation source and transmitted through the subject; and 
 a support mechanism configured to support the first radiation source, the first detector, the second radiation source, and the second detector so as to make the first radiation source, the first detector, the second radiation source, and the second detector rotate about the same rotation axis such that the first radiation source and the first detector face each other through the subject, and the second radiation source and the second detector face each other through the subject. 
 
     
     
       7. The radiotherapy system of  claim 6 , wherein the counting processing unit generates second counting data included in preset another energy range based on a second output signal from the second detector. 
     
     
       8. The radiotherapy system of  claim 7 , wherein the image generating unit generates data of a second medical image based on the second counting data. 
     
     
       9. The radiotherapy system of  claim 8 , further comprising a display unit configured to display the first medical image and the second medical image side by side. 
     
     
       10. The radiotherapy system of  claim 1 , further comprising a post-collimator mounted on the first detector,
 wherein the post-collimator includes X-ray shielding plates configured to remove scattered rays and radially arrayed about an X-ray focus of the first radiation source. 
 
     
     
       11. The radiotherapy system of  claim 1 , further comprising a support mechanism configured to support the first radiation source, the first detector, and the second radiation source so as to make the first radiation source and the first detector face each other through the subject. 
     
     
       12. The radiotherapy system of  claim 1 , further comprising:
 a first support mechanism configured to support the first radiation source so as to allow the first radiation source to move along a first circumferential orbit centered on a predetermined axis; 
 a second support mechanism configured to support the first detector so as to allow the first detector to move along a second circumferential orbit centered on the predetermined axis; and 
 a controller configured to synchronously control the first support mechanism and the second support mechanism to move the first radiation source along the first circumferential orbit and move the first detector along the second circumferential orbit and to perform X-ray imaging at a plurality of radiation angles around the predetermined axis during movement of the first radiation source so as to perform tomosynthesis imaging, 
 wherein the image generating unit reconstructs tomosynthesis image data associated with the subject based on a plurality of medical images corresponding to the plurality of irradiation angles. 
 
     
     
       13. A radiotherapy system comprising:
 an X-ray generator configured to generate X-ray photons; 
 an X-ray detection unit configured to detect X-ray photons generated from the X-ray generator and transmitted through a subject in a photon counting mode; 
 an extraction unit configured to extract specific output data associated with X-ray photons belonging to a specific energy region from output data from the X-ray detection unit by using a threshold preset for the specific energy region; 
 a reconstruction unit configured to reconstruct CT image data expressing a spatial distribution of CT values of a substance corresponding to the specific energy region based on the specific output data; and 
 a radiotherapy planning unit configured to decide a radiotherapy parameter associated with a radiotherapy for the subject by using the CT image data, wherein 
 the extraction unit is configured to extract the specific output data with a reduced noise component from output data from the X-ray detection unit by using a threshold set to an energy value corresponding to a window band which has an incident X-ray peak energy at its center and an energy width corresponding to an energy resolution, the reduced noise component being of an energy region lower than the threshold. 
 
     
     
       14. The radiotherapy system of  claim 13 , wherein the specific energy region is set to an energy region to which primary X-rays of X-ray photons detected by the X-ray detection unit belong. 
     
     
       15. The radiotherapy system of  claim 13 , wherein the extraction unit extracts the specific output data from the output data by removing an energy component of noise originating from an electronic circuit mounted on the X-ray detection unit from the output data. 
     
     
       16. The radiotherapy system of  claim 13 , wherein the specific energy region is set to an energy region to which a K-absorption edge of a specific substance existing in the subject out of X-ray photons detected by the X-ray detection unit belongs. 
     
     
       17. The radiotherapy system of  claim 16 , wherein the specific substance comprises at least one of a bone, a contrast agent, water, and another component. 
     
     
       18. The radiotherapy system of  claim 17 , further comprising an image processing unit,
 wherein the extraction unit extracts bone data associated with an energy region to which a K-absorption edge of the bone as the specific output data belongs from the output data, 
 the reconstruction unit reconstructs, as the CT image, bone image data expressing a spatial distribution of CT values of the bone based on the bone data, and 
 the image processing unit calculates a spatial positional shift amount between the bone image and a CT image generated immediately before the radiotherapy. 
 
     
     
       19. The radiotherapy system of  claim 18 , further comprising:
 a radiation source configured to generate radiation; 
 a support body configured to mount the radiation source thereon; 
 a rotation support mechanism configured to support the support body so as to allow the support body to rotate; 
 a first driver configured to generate power for driving the rotation support mechanism; 
 a top configured to place the subject thereon; 
 a top support mechanism configured to support the top so as to allow the top to freely move; 
 a second driver configured to generate power for driving the top support mechanism; and 
 a controller configured to control the first driver and the second driver to move the top and the support body in accordance with the positional shift amount and to match a spatial position of the subject at the time of imaging of the CT image immediately before the radiotherapy with a spatial position of the subject at the time of imaging of the bone image. 
 
     
     
       20. A radiotherapy system comprising:
 a first radiation source configured to generate radiation having a first energy; 
 a first detector configured to detect radiation generated from the first radiation source and transmitted through a subject; 
 a second radiation source configured to generate radiotherapy radiation having a second energy larger than the first energy; 
 a second detector configured to detect radiation generated from the second radiation source and transmitted through the subject; 
 a rotation support mechanism configured to support the first radiation source, the first detector, the second radiation source, and the second detector so as to make the first radiation source, the first detector, the second radiation source, and the second detector rotate about the same rotation axis such that the first radiation source and the first detector face each other through the subject, and the second radiation source and the second detector face each other through the subject; 
 a counting processing unit configured to obtain counting data included in a preset energy range based on a first output signal from the first detector; 
 an image generating unit configured to generate data of a medical image associated with the subject based on the counting data; and 
 
       a calculation unit configured to calculate an index value associated with a body motion amount of the subject by using the medical image, wherein
 the counting processing unit comprises 
 a data acquisition unit configured to acquire the first output signal from the first detector in a photon counting mode and generate first acquired data based on the first output signal, and 
 an extraction unit configured to extract first counting data with a reduced noise component from the first acquired data by using a threshold set to an energy value corresponding to a window band which has an incident X-ray peak energy at its center and an energy width corresponding to an energy resolution, the reduced noise component being of an energy region lower than the threshold. 
 
     
     
       21. The radiotherapy system of  claim 1 , wherein the extraction unit is configured to set the threshold to a lower limit of the window band. 
     
     
       22. The radiotherapy system of  claim 1 , wherein the extraction unit is configured to determine the threshold based on an energy resolution of the first detector, flux of incident X-rays, and an energy distribution of incident X-rays.